1. Field of Invention
Apparatuses and methods consistent with the present invention relate to a light emitting apparatus and a control method therefor, and more particularly, to a light emitting apparatus which minimizes power consumption of a switching part, and a control method therefor.
2. Description of the Related Art
Generally, a cathode ray tube (CRT) and a flat panel display (FPD) have been used for a display apparatus. Also, a liquid crystal display (LCD), a plasma display panel (PDP), an organic light emitting diode (OLED), a digital light processing (DLP), etc. have been used for the FPD.
Here, the LCD, the DLP, etc. use a light emitting element such as an light emitting diode (LED) or the like as a light source of a back light unit. The LED is a point light source having high brightness and superior color reproduction. For enhancing the quality of a display image, a light emitting apparatus driven by current such as the LED should minimize a ripple of an output current, and needs a driving unit having a rapid response. Here, a current source operating in a linear type is used as the driving unit.
When a light emitting part of a related art light emitting apparatus normally operates, a power supplying part supplies a voltage having a predetermined level. The supplied voltage is applied to the light emitting part and a switching part. Thus, a voltage across the switching part depends on a voltage across the light emitting part. Referring to FIG. 5, if a voltage VL across the light emitting part decreases, a voltage Vd across the switching part increases.
As the voltage Vd across the switching part increases, the power consumption thereof increases. Especially, in case of LEDs having high brightness used for a light source of a display apparatus, there may be different voltages for the same current, respectively. Thus, a driving voltage should be set so as to be sufficient in consideration of the variation.
Also, if there occurs a damage such as a short circuit of an LED in the light emitting apparatus, a voltage corresponding to a forward voltage drop of the short circuited LED is all applied to the switching part, and accordingly, thus the switching part continues to perform current control.
Also, if a surrounding temperature of an LED is low, a voltage across the LED sensitively decreases as it continues to be driven. If a surrounding temperature thereof is high or the LED is again driven after halting, voltage across the LED sensitively increases. As described above, in the related art light emitting apparatus, a voltage across the switching part varies markedly according to voltage variation due to a damage of the light emitting part such as the LED, voltage deviations among the respective light emitting parts, and voltage variation of the light emitting part due to temperature variation of the light-emitting part.